Credit: Josh Reynolds/AP

Susan Kaplan: Congresswoman Niki Tsongas, announcing today that she will not seek reelection next year. Tsongas represents Massachusetts 3rd District which covers portions of Worcester, Essex and Middlesex Counties including her home of Lowell. Tsongas has served in Congress since 2007 when she won a special election to fill the seat of Marty Meehan who resigned to become the chancellor of UMass Lowell. He now leads the whole UMass system. Tsongas was the wife of the late Paul Tsongas who himself represented Massachusetts in the House and then the Senate. He died in 1997. Joining us now on the line to take a look at Tsongas’ time in Congress is WGBH News contributor David Bernstein. Hi David.

David Bernstein: Hi. How are you, Susan?

Susan Kaplan: Good, thank you. So why has Congresswoman Tsongas chosen not to run for a new term?

David Bernstein: Well we don't really know. She put out a statement that really didn't say much other than, you know, that she's enjoyed her time in Congress and she thinks that this is the right time. But, there was always a sense that she would not necessarily hold that seat for a very long time. She was already over 60 at the time. She seems very healthy and spirited when I've seen her over the last couple of years. It did take a lot of people by surprise who I've talked to today, but she seems to be ready to move on to something else.

Susan Kaplan: What has she accomplished during her tenure in Congress? What's her track record?

David Bernstein: The thing that she's probably best known for is her work on sexual assault in the military. She's really been a leading voice on providing oversight, adding some legislation and also sort of forcing it as an issue from her seat on the Armed Services Committee. I would also point to work she's done on the environmental issues: conservation, rivers, and preservation of species and so forth. I've talked to her a number of times over the years on that, and she's really very passionate about it.

Susan Kaplan: How has she done with her constituents?

David Bernstein: She was elected with some votes from all around the district and she ended up being very very popular [and] has only gotten token opposition in recent years.

Susan Kaplan: What about her legacy — what do you think that will be?

David Bernstein: Well, she's always going to be mixed up and caught up with the legacy of her husband Paul Tsongas, the late Paul Tsongas, who is sort of legendary in Massachusetts. You know, senator, ran for president, was really a big name in the state and she's always to some extent going to be looked at as the widow of and she understands that, she accepts that as part of her legacy. But I think if you look around Lowell and the rest of that district, there's a lot that's changed for the better in those cities and towns that I think she can take some credit for.

Susan Kaplan: Who do you see running for her seat in next year's election?

David Bernstein: There are a lot of names being talked about including several of the people who lost to Niki Tsongas back in that 2007 special election. Eileen Donahue, who was the mayor of Lowell and is now a state senator. Jamie Eldridge, who is another state senator who was a state representative at the time. Also possibly Steve Kerrigan who looked at running back then and, I'm told, will be looking at it again. But there are also a number of younger folks around the district: state representatives, mayors, a lot of interesting and diverse faces around the district. And of course several Republicans who will take a look at the race too.

Susan Kaplan: What if any impact does this have on the wider election in Massachusetts next year. Governor Baker will be seeking re-election as well as Senator Elizabeth Warren and now there will be a contest for the open seat in the U.S. House.

David Bernstein: That's right. And in some ways, the House race will be down ballot and impacted by those big marquee statewide races. But I can also see it working the other way around where there could be a lot of interest in this race for who's going to win this congressional seat. And that could actually drive a lot of turnout that could affect those top of the ballot races. I think you're going to see a lot of interest in the primaries on both sides. And I think the primary on the Republican side in this race as well as the statewide Senate race could end up being something of a proxy for this sort of “Charlie Baker, moderate, anti-Trump" Republicans versus the sort of more conservative, more pro-Trump Republicans. I think you could see that playing out in the primaries. Who wins that will determine what the race looks like in the general election.

Susan Kaplan: OK, well thanks for joining us, David.

David Bernstein: My pleasure.

Susan Kaplan: That's WGBH News contributor David Bernstein. This is All Things Considered.